I am not sure whether the prosecution is cruelly and dishonestly trying to put an innocent man in prison, or if it is trying to throw the case so Zimmerman gets a public acquittal. It is baffling. It reminds me of family court where I often think that officials cannot really believe that nonsense that they are espousing, except that I never think that they are deliberately throwing the case.

Di Maio is an excellent witness, in contrast to the medical examiner Bao. He is clear, unambiguous, and convincing. He sticks to his expertise. He backs up what he says with explanations of the relevant science and medicine, and how the evidence backs that up.

A regular (fact) witness just tells what he say, with no opinions or conclusions. An expert witness is allowed to give opinions and conclusions.

A bad expert witness gives opinions and conclusions, and demands that you accept them because of his credentials and experience. A good expert witness teaches the relevant science or medicine to the jury, as it is generally accepted in the textbooks, and then the jury understands the conclusion as does not need to trust the expert's impartiality or judgment.

I was amazed at how badly the prosecutor misunderstands the role of the expert. From the trial today:

Prosecutor Bernie de la Rionda: In order to give an opinion, when someone gives you a hypothetical, it has to based on facts that are accurate and truthful, correct?

Di Maio: A hypothetical doesn't have to be true. A hypothetical is just "suppose this and this happened ...".

Prosecutor Bernie de la Rionda: So we would be speculating, I guess, or potentially speculating?

Di Maio: It is not even speculating. You are giving a presentation and asking what it is.

Di Maio is correct. An excellent expert witness could testify entirely by answering hypothetical questions, and never even look at the facts of the case. For example, a witness might be useful just answering these hypothetical questions: "What does a gunshot would look like if the gun is pressed against the skin? If the gun is 3 inches away? 12 inches? 24 inches? How is that known?" The jury could then apply his knowledge to the facts of the case.

Di Maio focused on one question: Is the objective evidence (autopsy report, pictures, etc) consistent with the reenactment that Zimmerman gave to the police? The answer is yes. The gun was up against the fabric of Trayvon's hoodie and 2 to 4 inches away from his chest. Apparently Trayvon was leaning forward with the hoodie 2-4 inchies down. Zimmerman had at least 6 identifiable injuries to the head, and probably a broken nose and a mild concussion.

In family court, psychologists will sometimes testify as experts and recommend a child custody schedule. That is allowed, but is worthless unless the witness can explain why the generally accepted knowledge facors that schedule over alternative schedule. The psychologists are usually not able to do that. He should also answer hypothetical questions, such as "if the parent drank less beer, you would that affect your schedule?" Again, they are unable or unwilling to spell out their prejudices.

Update: Lou Dobbs compares the trial to a "Soviet show trial", and says, "there is no doubt that Florida authorities are now fear-struck by threats of mob violence if that trial does not go their way." They are making a video to persuade the blacks not to riot. He also says the lack of evidence against Zimmerman shows a "travesty of political corruption, pandering, and disregard for the rights of an American citizen."